1. Field of the Invention
The present invention relates to a semiconductor device having semiconductor structure bodies on its upper and lower surfaces, and a method of manufacturing the semiconductor device.
2. Description of the Related Art
A conventional semiconductor device, which is disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2001-339011, has such a structure that a semiconductor structure body including a semiconductor substrate and a plurality of external connection terminals provided under the semiconductor substrate, is mounted on a base board by a face-down method. In this case, the external connection electrodes of the semiconductor structure body which is mounted on the base board, are connected to lower-layer wirings provided on a lower surface of the base board, through vertical conductors formed in the substrate. The lower surfaces of the base board and the lower-layer wirings are provided with an overcoat film having opening portions at parts corresponding to connection pad portions of the lower-layer wirings. Solder balls are provided in the opening portions of the overcoat film and under the opening portions, and are connected to the connection pad portions of the lower-layer wirings.
In the above-described conventional semiconductor device, the solder balls are bonded to connection terminals which are provided on a main circuit board (motherboard). Thereby, the semiconductor device is mounted on the main circuit board.
In many cases, a plurality of electronic components, including other semiconductor structure bodies and chip components, are mounted on the main circuit board. In such a case, the size of the main circuit board becomes relatively large.
In the meantime, in order to reduce the size of the main circuit board, it is thinkable to mount such electronic components, including other semiconductor structure bodies and chip components, under the base board of the conventional semiconductor device. In this type of semiconductor device, in order to bond the solder balls, which are provided under the base board, to the connection terminals on the main circuit board, it is necessary to make the height of each solder ball greater than the height of the electronic components mounted under the base board, and there is such a problem that the diameter of the solder hall increases, the pitch of arrangement of solder balls increases, and the reduction in pitch is limited.